21307776 has 64 divisors (see below), whose sum is σ = 64692480. Its totient is φ = 6087168.

The previous prime is 21307771. The next prime is 21307807. The reversal of 21307776 is 67770312.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21307771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1276 + ... + 6651.

It is an arithmetic number, because the mean of its divisors is an integer number (1010820).

Almost surely, 2^21307776 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21307776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32346240).

21307776 is an abundant number, since it is smaller than the sum of its proper divisors (43384704).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21307776 is an equidigital number, since it uses as much as digits as its factorization.

21307776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7951 (or 7939 counting only the distinct ones).

The product of its (nonzero) digits is 12348, while the sum is 33.

The square root of 21307776 is about 4616.0346619149. The cubic root of 21307776 is about 277.2337125759.

The spelling of 21307776 in words is "twenty-one million, three hundred seven thousand, seven hundred seventy-six".